Igniter for two-cycle multi-cylinder engine

ABSTRACT

An igniter for a multi-cylinder engine comprises a plurality of ignition circuits each consisting of a breaker, an ignition coil and a spark plug. The circuits are connected in series to one another and to one end of an ignition generator coil of an engine driven magneto. The ends of the ignition circuits and the other end of the ignition generator coil are grounded.

Unite States Faieni 1 Shino et al.

1451 Sept. 18,1973

1 1 IGNITER FOR TWO-CYCLE MULTl-CYLINDER ENGINE [76] lnventors: GoroShino; Katsuyuki Okamoto; Katsumi Shimura, all of Sawafuji DenkiKabushiki Kaisha, l0, 6-chome, Maino-cho, ltabashi-ku, Tokyo, Japan [22]Filed: Oct. 22, 1971 [21] Appl. No.: 191,607

52 us. 121...... 123/148 E, 123/148 R, 123/149 R, 123/148 AC, 123/149 A,123/148 DC,

51 Int. Cl. F02p 1/00 [58] Field of Search 123/148 R, 148 E, 123/149 R,149 A,148 AC, 148 DC, 148 DS [56] References Cited UNITED STATES PATENTS3,576,183 4/1971 Miyamoto 123/148 2,256,907 9/1941 Ochscnbcin 123/1493,464,397 9/1969 Burson 123/149 2,845,850 7/1958 Kongsted 123/1492,047,431 7/1936 Randolph 123/148 Primary ExaminerLaurence M. GoodridgeAssistant ExaminerRonald B. Cox Attorney-Arthur G. Connolly et a1.

[57] ABSTRACT An igniter for a multi-cylinder engine comprises aplurality of ignition circuits each consisting of a breaker, an ignitioncoil and a spark plug. The circuits are connected in series to oneanother and to one end of an ignition generator coil of an engine drivenmagneto. The ends of the ignition circuits and the other end of theignition generator coil are grounded.

5 Claims, 4 Drawing Figures PATENTED SEN 8'91! SHEET 1 BF 2 IGNITER FORTWO-CYCLE MULTI-CYILINDER ENGINE BACKGROUND OF THE INVENTION The presentinvention relates to an igniter for a twocycle multi-cylinder engine.

There are two types of igniters for a two-cycle multicylinderengine--battery type and flywheel magneto type. In the flywheel magnetotype the electric output of the flywheel magneto driven by the torque ofthe engine is tapped separately for each of the multi-split coils. Thealternating electromotive forces generated in the plural coils of theflywheel magneto are each connected to the primary winding of a boostercoil of which the secondary winding is connected to the spark plug.Moreover, the coil of the above-mentioned flywheel magneto, a breaker toshort-circuit this circuit and a capacitor efiective to prevent thesparks generated with the breaker action from generating a noise radiowave are connected in parallel to the primary winding of the boostercoil.

In such conventional igniters there must be as many spark plugs asflywheel magneto coils, and there is no interchangeability betweenengines designed with different numbers of cylinders. Also, the numberof capacitors for noise elimination must be the same as the number ofcylinders.

Another drawback to conventional igniters is that when the engine ismanually or otherwise rotated in the wrong direction by mistake, theengine continues to run in the wrong direction.

SUMMARY OF THE INVENTION Accordingly, it is an object of the presentinvention to provide a circuit that makes it possible to apply the sameflywheel magneto toseveral types of engines differing in the number ofcylinders whereby it is impossible for the engine to rotate in the wrongdirection and a single capacitor suffices for noise elimination.

In accordance with the present invention an ignition is provided for amulti-cylinder engine comprising a plurality of ignition circuits eachconsisting of a breaker and ignition coil and a spark plug. The circuitsare connected in series to one another and to one end of an ignitiongenerator coil of an engine driven magneto. The ends of the ignitioncircuits and the other end of the ignition generator coil are grounded.

Also, a diode may be connected between the ground and the ignitiongenerator coil. Alternatively, the diode may be connected between theignition generator coil and the plurality of ignition circuits.Moreover, the junction between the ignition generator coil and theplurality of ignition circuits may be connected to one end of acapacitor with the other end of the capacitor connected to a ground.

BRIEF DESCRIPTION OF THE DRAWINGS Novel features and advantages of thepresent invention in addition to those mentioned above will becomeapparent to those skilled in the art from a reading of the followingdetailed description in conjunction with the accompanying drawingwherein:

FIG. 1 is a schematic elevational view of a flywheel magneto accordingto the present invention;

FIG. 2 is a wiring diagram for a flywheel magneto according to thepresent invention;

FIG. 3 is a wiring diagram for another embodiment of the presentinvention; and

FIG. 4 is a diagram comparing the working principle of the presentinvention with a conventional device.

DETAILED DESCRIPTION OF THE INVENTION Referring in more particularity tothe drawing, FIG. I illustrates one embodiment of the present inventionincluding a flywheel type magneto I attached to a three-cylindertwo-cycle engine (hereinafter referred to as the engine) and driven insynchronism with the engine crankshaft 6, and a main assembly 2 of theflywheel for the magneto I. The main assembly of flywheel 2 isfabricated of magnetic material like iron plate and shaped in the formof a disk.

On the inside cylindrical surface of the main assembly of flywheel 2there are positioned six magnets 3, each magnetized in the radialdirection, together with pole pieces 4 such that magnets with differentpolarities may be next to one another. Item 5 is a breaker opening andclosing cam, and this cam and the above mentioned main assembly offlywheel are fixed to the engine crankshaft 6. A stator plate 7 isattached to the engine crankcase (not shown), and three cores 10, ll, 12are fitted at equal intervals on the stator plate. Cores 10, II and 12are respectively attached to the ignition generator coil 8, the charginggenerator coil 9 and the ignition generator coil 13 in such manner thatthey may magnetically oppose the six magnets 3 of the above mentionedmain assembly of flywheel 2.

Also, on the stator plate 7 are fitted the breakers 17, I8, 19 for theignition circuits 30, 31, 32 (shown in FIG. 2) of the first, second andthird cylinders; the spark eliminating capacitor 20 for these breakers;and the diode 21. As indicated in FIG. 4 (a) (b) (c), the cam 5 sets theopening crank angles a 01 a of the breakers 17, 18, 19 at about 60 andthe opening positions at about 30 ahead of the crank angles 0 (piston attop dead center) respectively of the first, second and third cylindersof the engine. FIG. 2 is a wiring diagram of the device of oneembodiment of the invention in which the first, second and thirdcylinders of the engine can be ignited in succession at approximatelyequal intervals by the power generated in the ignition generator coil ofthe flywheel type magneto 1 shown in FIG. 1. In FIG. 2, 23, 24, 25denote the three ignition coils provided on the outside of the magneto land they consist respectively of primary coils 23a, 24a, 25a andsecondary coils 2312, 243b, 2512. The primary coils 23a, 24a, 25a areconnected to the breakers 17, 18, I9, and the secondary coils 23b, 24b,251; are connected to spark plugs 27, 28, 29, thereby respectivelyconstituting the ignition circuits 30, 31, 32 for the first, second andthird cylinders. In this manner, the breakers 17, 18, 19 of the ignitioncircuits 30, 3t, 32 are connected in series, one end being grounded andthe other end being connected in series to one end of the ignitiongenerator coil 13 of the magneto l. The other end of the ignitiongenerator coil I3 is grounded via the diode 21. One end of the capacitor20 is connected to the junction between the ignition circuit 30 of thefirst cylinder and the ignition generator coil 13, and the other end isgrounded.

The operation of the device is as follows. Assuming the engine isrotating in the direction of the arrow of FIG. d, the six magnets 3 ofthe flywheel 2 cause positive voltages V V V and negative voltages V,',V V of the wave forms illustrated in FIG. 4 (d) to be generated in theignition generator coil 13. Then in the circuit comprising the ignitiongenerator coil i3, ignition circuits 30, 31, 32 of the first, second andthird cylinders and diode 2i, currents flow having wave forms a,, a a asillustrated in FIG. 4 (c), with the negative voltages V V V suppressedby the diode 21 and the generating positions of the currents laggingabout 30 behind the generating positions of the positive voltages V,, VV due to the impedance of the ignition generator coil 13. When the timecomes for ignition of the first cylinder and the breaker 17 of theignition circuit of the first cylinder opens at the point (FIG. 4 (2.)),i.e., about 30 ahead of the crank angle of the first cylinder (withpiston at top dead center), a current a, having a wave form asillustrated in FIG. 4 (f) flows suddenly in the primary coil 23a of theignition coil 23. As a result, a high voltage occurs in the secondarycoil 23b whereby ignition is effected by a high voltage spark generatedin the spark plug 27 of the first cylinder. The breaker 17 closes at thepoint t, (FIG. 4 (a)), i.e., at about a 30 crank angle of the firstcylinder.

Next, when the time comes for ignition of the second cylinder and thebreaker 18 for the ignition circuit 31 of the second cylinder opens atthe point 2, (FIG. 4 (b)), i.e., about 30 ahead of the crank angle 0 ofthe second cylinder, a current a having a wave form as illustrated inFIG. 4 (g) suddenly flows in the primary coil 24a of the ignition coil24. As a result, a high voltage occurs in the secondary coil 24b wherebyignition is efi'ected by a high voltage spark generated in the sparkplug 28 of the second cylinder. The breaker l8 closes at r,', i.e.,about a 30 crank angle of the second cylinder.

Then as the time comes for ignition of the third cylinder and thebreaker 19 for the ignition circuit 32 of the third cylinder opens at i(FIG. 4 (c)), i.e., about 30 ahead of the crank angle 0 of the thirdcylinder, a current a;,' having a wave form as illustrated in FIG. 4 (h)suddenly flows in the primary coil 25a of the ignition coil 25. As aresult, a high voltage occurs in the secondary coil 25b whereby ignitionis effected by a high voltage spark generated in the spark plug 29 ofthe third cylinder. The breaker l9 closes at t;,, i.e., about a 30 crankangle of the third cylinder. Through repetition of the above process,the first, second and third cylinders of the engine are successivelyignited to rotate the engine in the right direction for continuousoperation.

If by mistake the engine is rotated by hand or other means in a wrongdirection as indicated by the broken arrow of FIG. 4, the six magnets 3of the flywheel 22 cause the positive voltages V V V and negativevoltages V,,', V,,', V each having a wave form as illustrated in FIG. 4(i) to be generated in the ignition generator coil H3 in the order of VV V V V V,, from right to left in the drawing. Then, in the circuitcomprising the ignition generator coil 13 ignition circuits 30, 31, 32of the first, second and third cylinders, and diode 21, currents flowhaving wave forms a a a as illustrated in FIG. 4 (j), with the negativevoltages V,,', V,,, V,,' suppressed by the diode 2i and the generatingpositions of the currents lagging about 30 behind the positive voltagesV V V Therefore, even if the breaker 19 for the ignition circuit 32 ofthe third cylinder opens at i as indicated in FIG. 4 (o), no currentflows in the breaker 19 as seen from FIG. 4 (j), and accordingly nocurrent flows in the primary coil 25a of the ignition coil 25. Thus, novoltage occurs in the secondary coil 25!), and accordingly, with nospark flying in the spark plug 23 of the third cylinder, the thirdcylinder is not ignited. The breakers l3, I? for the ignition circuits31, 30 of the second and first cylinders, even if opened at r,', t, asindicated in FIG. 4 (b) (a), do not cause ignition in the same manner aswith the ignition circuit 32 of the third cylinder. Thus there is nopossibility of the engine being rotated in the wrong direction.

Next, another embodiment of the present invention as illustrated inFllG. 3 is described below.

Whereas in the embodiment illustrated in FIG. 2 a diode 21 is connectedin series with the ignition generator coil R3 to prevent the negativevoltage from being impressed on the ignition circuits 30, 31, 32 of thefirst, second and third cylinders, in the embodiment illus trated inFIG. 3 a diode 21' is connected in parallel with the ignition generatorcoil 13 to short circuit the negative voltage generated in the coil 113to the diode 2i This prevents the negative voltage from being impressedon the ignition circuits 30, 31, 32 of the first, second and thirdcylinders. Otherwise, the construction and performance are the same asin the embodiment in FIG. 2.

In the event the diode 21 of FIG. 2 is deleted from the circuit andshort circuited, with this further embodiment of the invention, just asin the embodiment using the diode, there is no relation between thenumber of ignition generator coils in the flywheel magneto and thenumber of spark plugs, and no trouble arises when the engine is rotatedin the right direction. However, when the engine is mistakenly rotatedin a wrong direction the positive voltages V V V and the negative voltages V V V of the same wave form as occur in the diode igniterembodiment of the present invention are generated in the order of V V VV,,', V V from right to left in the drawing. Then the above mentionedpositive and negative voltages are impressed on the ignition circuits30, 31, 32 of the first, second and third cylinders which have no diodeconnected in series or in parallel with i the ignition genei ator 53ersin the above mentioned case. Due to the impedance of the ignitiongenerator coil 13, with the generating position lagging about 30 behindthe positive and negative voltages, positive currents a a a and negativecurrents a a ai having a wave form as illustrated in FIG;

4 (k) flow from right to left in the drawing in the order of a a a a a aAs a result, the opening po-- sitions t t 1 of the breakers l7, l8, 19for the igni tion circuits 30, 3t, 32 of the first, second and thirdcylinders as shown in FIG. 4 (a) (b) (0) agree with the generatingpositions of the negative currents o a a Thus, when the breakers 17, 18,19 open, the cur-- rents a a a having wave forms as illustratedrespectively in FIG. 4 (l) (m) (n) flow in the primary coils 23a, 2%,25a of the ignition coils 23, 2d, 25. Thereupon a high voltage occurs inthe secondary coils 23b, 25b, 25b, and as a result a high voltage sparkin the spark plugs 27, 28, 29 ignites the first, second and thirdcylinders. Thus, there is a possibility of the engine being rotated in awrong direction, and this is the same as in conventional devices. Thepossibility of the engine running in a wrong direction may be eliminatedif the breaker opening position in wrong running or the breaker closingposition in right running is shifted closer to the position where aspark cannot ignite any cylinder, for example, to an engine crank angleof (with piston at bottom dead center). In other words, the openingangles a,a,a, of the breakers l7, l8, 19 shown in FIG. 4 (a) (b) (c) arewidely enlarged. But in that case the currents a,, 1,, a flowing in theignition generator coil 13 shown in FIG. 4 (e) (same as the currentsflowing in the ignition circuits 30, 31, 32) will drop and the ignitionefficiency will somewhat deteriorate as compared to the case of using adiode as in one embodiment of the invention.

According to one embodiment of the present invention, the igniter has adiode connected in series or in parallel with the ignition generatorcoil to impress an AC half wave voltage on the ignition circuit of eachcylinder. The ignition efficiency of each cylinder does not deterioratenor is there any possibility of any cylinder of the engine being ignitedthrough a mistake in manually or otherwise turning the engine. Thus,running of the engine in the wrong direction is prevented.

The above explanation of the invention applied to a three-cylinder,two-cycle engine, but it goes without saying that the present inventionis applicable to any multi-cylinder two-cycle engine.

What is claimed is:

1. An igniter for a multi-cylinder engine comprising a flywheel assemblysecured to an engine crankshaft, a plurality of equally spaced apartmagnets arranged in circular fashion on the inside cylindrical surfaceof the flywheel assembly with each magnet magnetized in a radialdirection relative to the engine crankshaft, a stator plate and anignition generator coil positioned inside the flywheel assembly on thestator plate, a cam fixed to the engine crankshaft, a plurality ofbreakers fitted on the stator plate constructed and arranged for openingand closing by the cam, a plurality of ignition circuits each having apair of primary and secondary coils constructed and arranged to generatea high tension voltage through the intermittent opening and closing ofthe breakers, the primary coils in the ignition circuits being connectedto the breakers and the secondary coils being connected to spark plugs,and the breakers of the ignition circuits being connected in series withone end grounded and the other end connected to the ignition generatorcoil.

2. An igniter for a multi-cylinder engine as in claim 1 wherein theother end of the ignition generator coil is connected to the plus sideof a diode, the minus side of which is grounded.

3. An igniter for a multi-cylinder engine as in claim 1 wherein thejunction between the ignition generator coil and the plurality ofignition circuits is connected to one end of a capacitor, the other endof which is grounded.

4. An igniter for a multi-cylinder engine as in claim 1 wherein thejunction between the ignition generator coil and the plurality ofignition circuits is connected to the plus side of a diode, the minusside of which is grounded.

5. An igniter for a multi-cylinder engine as in claim 2 wherein thejunction between the ignition generator coil and the plurality ofignition circuits is connected to the plus side of a diode, the minusside of which is grounded.

i i I! i UNITED STATES PATENT @FFICE CERTIFICATE OF CGREECTION Patent N:33759,237 Dated September 18, 1973 Inventor) Goro Shino et al It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

On the Front Page, insert Assignee: Sawafuji Denki Kabushiki Kaisha,

Tokyo, Japan Foreign Application Priority Data December 2 1970 Japan5-118mm Signed and sealed this 26th day of March 1974.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. C. MARSHALL DANN Attesting Officer Commissioner ofPatents

1. An igniter for a multi-cylinder engine comprising a flywheel assemblysecured to an engine crankshaft, a plurality of equally spaced apartmagnets arranged in circular fashion on the inside cylindrical surfaceof the flywheel assembly with each magnet magnetized in a radialdirection relative to the engine crankshaft, a stator plate and anignition generator coil positioned inside the flywheel assembly on thestator plate, a cam fixed to the engine crankshaft, a plurality ofbreakers fitted on the stator plate constructed and arranged for openingand closing by the cam, a plurality of ignition circuits each having apair of primary and secondary coils constructed and arranged to generatea high tension voltage through the intermittent opening and closing ofthe breakers, the primary coils in the ignition circuits being connectedto the breakers and the secondary coils being connected to spark plugs,and the breakers of the ignition circuits being connected in series withone end grounded and the other end connected to the ignition generatorcoil.
 2. An igniter for a multi-cylinder engine as in claim 1 whereinthe other end of the ignition generator coil is connected to the plusside of a diode, the minus side of which is grounded.
 3. An igniter fora multi-cylinder engine as in claim 1 wherein the junction between theignition generator coil and the plurality of ignition circuits isconnected to one end of a capacitor, the other end of which is grounded.4. An igniter for a multi-cylinder engine as in claim 1 wherein thejunction between the ignition generator coil and the plurality ofignition circuits is connected to the plus side of a diode, the minusside of which is grounded.
 5. An igniter for a multi-cylinder engine asin claim 2 wherein the junction between the ignition generator coil andthe plurality of ignition circuits is connected to the plus side of adiode, the minus side of which is grounded.